FIGS. 1 and 2 illustrate one known form of frame rail incorporated into a chassis of a recreational vehicle such as for a Winnebago® motorhome. The construction of FIGS. 1 and 2 include spaced apart parallel frame rails 10,12 which are interconnected by a plurality of cross-members, one being indicated at 14 in FIG. 2. A front suspension 16 is coupled to the frame rails 10,12 and also to an axle structure 18 which carries first and second wheels and tires 20,22. A rear suspension 24 is coupled to the frame rails 10,12 and supports and axle and tandem wheel structure 26 toward the rear of the chassis.
The frame rails of FIGS. 1 and 2 are generally of a C-shaped configuration with upper and lower inwardly extending flanges interconnected by an upright or vertical web. The frame rails of FIGS. 1 and 2 have a height H1 which in one specific known embodiment is 9 inches. The height H1 is constant along the full length of each of the frame rails 10,12.
A clearance C1 exists between the underside of frame rails 10,12 and the ground 30 adjacent to front wheels 18. In addition, a clearance C2 exists between the underside of frame rails 10,12 and the ground 30 adjacent to the rear wheels 26. In known constructions, C2 may be slightly greater than C1. The actual clearances C1 and C2 vary with the tire size and suspension that is being used. For example, an average clearance in the section between the front and rear wheels 18,26 between the underside of the frame rails and ground in one known construction is 25 inches.
Another form of known chassis and frame rail construction for a recreational vehicle is shown in FIGS. 3 and 4. This configuration is known as a stacked rail configuration. Each frame rail 40,42 in FIGS. 3 and 4 is an assembly of three separate rail sections. Thus, frame rail 40 has a first upper or top rail section 44 which extends from a location 46 forwardly of a set of wheels and axle 48 to a location 50 which is rearwardly of a set of rear wheels and axle 52. At the forward end of the chassis, rail section 44 is stacked on top of a rail section 54 which extends from a location 56 rearwardly of the wheels 48 to a location 58 at the forward end of the chassis. In addition, the frame rail 40 has a lower rear frame rail section 60 which extends from a location 62 forwardly of the wheels 52 to a location 62 at the rear of the chassis. The lower front rail section 54 extends forwardly of the front end of rail section 44 while the rail section 62 extends rearwardly of the rear end 50 of the rail section 44. In one known construction, the height H2 of rail section 44 is 9 inches and the height H3 of each of the rail sections 54,60 is also 9 inches. Thus, the overall height H4 of the rail sections 44,54 (and of rail sections 44,60) is 18 inches. The rail sections 44,54 and 60 are also of a generally C-shaped configuration. The lower generally horizontal inwardly extending flange of rail section 44 is secured to the upper generally horizontal inwardly extending flange of rail section 54 and also to the upper generally horizontally inwardly extending flange of the rail section 60. Rail 42 in FIG. 4 is the mirror image of rail section 40 and is also a stacked three rail section assembly.
Assuming the clearance C4 of the FIG. 3 embodiment is the same as the clearance C1 in the FIG. 1 embodiment, then the average clearance C5 between the wheels 48 and 52 (and more specifically between ends 56 and 62 of the rail sections 54,60) is 9 inches greater than the average clearance between the wheels 18,26 of the FIG. 1 configuration. This allows for the positioning of under frame rail storage compartments for convenient storage of articles being transported by a user of the vehicle, such as a recreational vehicle having a body (not shown in these figures) mounted to the chassis depicted therein.
Although frame rail constructions for vehicles such as recreational vehicles are known, a need exists for improved frame rails for such vehicles and for chassis and vehicles incorporating such frame rails.